The objective of this proposal is to increase the clinical diagnostic value of color vision testing in ocular hypertensive and primary open-angle glaucoma (POAG) patients. This will be done by correcting color vision scores for the effects of variable lens density and uncontrolled retinal illuminance. In addition, we plan to investigate the clinical usefulness of a new method of color testing capable of isolating post-receptoral chromatic response, the low-frequency color test. Lens density correction factors and an optimal illuminance protocol will be developed from measurements made on normals, ocular hypertensive and glaucoma patients and on patients in the early stages of cataract formation. Color test performance will be measured using the Farnsworth Munsell 100-Hue, D-15 and desaturated D-15 tests and the new low-frequency color test. Individual lens density will be measured psycho-physically by comparing scotopic spectral sensitivity differences in the short wavelength spectral region to the known absorpton curve of rhodopsin, and photographically by comparing the energy in the 3rd and 4th Purkinje images reflected from the lens. True incidence rates of color vision loss specific to the disease process in POAG and ocular hypertensive patients will be determined. Low-frequency color testing may provide insight into the physiological mechanisms of damage in early and in later phases of glaucoma. The low-frequency technique will be adapted for routine patient use with a computer controlled color-monitor system. This study will also characterize the association of color loss with key visual field loss, visual acuity, and treatment status. A patient data base will be produced as a consequence of routine data storage during the study. This data base can support long term follow-up of ocular hypertensive and POAG patients in order to assess the prognostic value of color testing.